Sometimes clients do ask acousticians to obfuscate data, but this is strongly frowned on by the acoustics community. It's not going to perfectly represent the hearing of every individual. A weighting is not perfect, but it's a reasonable approximation. You have to bear in mind that everything in acoustics is subject to some degree of uncertainty. If you measured noise in dBZ you'd end up overestimating the perceived noise level. But is it a relatively simple engineering compromise - not a cover up. So, the A - weighting is not perfect, its aim is to mimic how sensitive humans are to sounds at different frequencies. Many of these are based on dBA to take into account which frequencies we hear better / worse.Īt very high levels dBC is sometimes used as we become more sensitive to low frequency sounds at higher pressures - all based on scientific evidence. There have been studies of this which inform regulation for noise at work - different depending on the country. louder sounds mean greater risk of hearing loss. Hearing damage / loss - a sound which provides a higher dBA measurement means the sound pressure waves being measured are stronger. Quite literally a 63 Hz pressure wave doesn't vibrate your eardrum / cochlea as much as a 1 kHz pressure wave. So there is a -26 dB correction at 63 Hz as we don't hear that well at that frequency compared to 1 kHz where no correction is added at all (the experiments are done relative to a 1 kHz tone). This is what the A weighting corrections you have linked to are showing. Sensitivity - so humans don't hear sound at all frequencies / pitches equally (and as you say we don't hear some pitches at all) - this is what the " tone experiments" show - they aren't meant to find out when people's hearing will be damaged, just find out which frequencies / pitches of sound we hear more / less keenly. so I don't really see how you can get hearing loss from that. if you can't hear a sound (and you have no current hearing damage), then the sound has not caused a vibration within your ear. > That's why inaudible noise at high SPL can be dangerous. I'd have to see the studies or evidence for correlating well with A-weighing. Even if it does correlate well, that is not to say that C,Z weighted can't reveal hazardous noise conditions when A-weighted can't -so C or better Z should be monitored on a regular basis. Since A-weighing is more about perceived loudness then why not wanna use Z-weighing when just in case when assessing NIHL risk? It's like why not just do it anyways.what are you afraid of finding? Even a person went to a doctor/audiologist and hearing test showed worse they likely would only have A weighted work data and regardless RELs are in A-weighted so only using A-weighted data they can "prove" it was because of noise, whereas any C,Z weighted data doesn't have (or lacks) any regulatory guidelines to support it was due to noise. C, Z weighing studies could be underrepresented not allowing for an opportunity to challenge this assertion. This could just be because A-weighing is used in RELs at work so most/all hearing damage reported is referenced to the A-weighted data. If an authority instead said "A-weighing underestimates SPL <1000Hz so we use Z-weighted decibels to ensure objectivity of SPL and not underestimate certain low-frequency noise hazardous environments" I'd figure people would say it makes sense and latch onto that as well. I have a suspicion that some authority said that and people are just latching on to it without thoroughly analyzing it. This is too ambiguous: "correlates well with A-weighting." Can you clarify? Damage to the stereocilia, however, does not heal. It does not necessarily result in permanent hearing loss, because the tympanic membrane can heal. Describing the stereocilia as “frequency-tuned oscillators” is not an uncontroversial description of how they work, but it’s serviceable.ĭifferent parts of this system can be damaged-you can get a tympanic membrane perforation (punctured eardrum), and this can be caused by actual raw ambient pressure. It’s definitely more complicated than what I’m describing, but that’s the gist of it. The short version is that sound pressure makes the tympanic membrane (eardrum) vibrate, and the ear transmits these vibrations eventually to the cochlea, which contains what can be thought of as a set of frequency-tuned oscillators (stereocilia) which translate sound pressure waves inside the cochlea into nerve impulses. If you’re not familiar with how the ear works, then the causes of hearing damage are definitely going to be mysterious. The answer to this is just going to be a regurgitation of “how does the ear work”. Second, if the cilia are not affected by raw pressure, then what kind of pressure are they affected by?
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